Question 1

Question 1:
Describe the characteristics used in hierarchial classification of organisms.

Accepted Answer

Answer:
Hierarchical system of classification was proposed by Linnaeus. In this classification, he arranged organisms into an ascending series of increasing inclusiveness forms. The taxonomic groups are arranged in a definite order, from higher to lower categories. Each category is called a taxon.

The taxa used in classifying organisms are:

(i) Species- It is the lowest category that includes individuals with similar morphological characteristics, which are able to breed among themselves and reproduce. For example, horse (Equus cabalus) and ass (Equus acinus) belong to the same genera Equus but are different species.

(ii) Genus- It includes related species which have less characteristics in common. Members of a genus have identical reproductive organs. For example, a banyan and a fig tree differ from each other in vegetative structures but resemble each other in reproductive organs, and thus they belong to the same genus Ficus.

(iii) Family- Group of related genera are included in a family. More similar genera are placed together in a single family. For example, a cat and a lion belong to the same family Felidae. They both possess similar structures and retractable claws.

(iv) Order- Families resembling one another in few characteristics are assembled in an order. For example, a tiger and a wolf share characteristics such as jaws with powerful incisors, large, sharp canines and carnivores. Thus they both belong to the same order Carnivora.

(v) Class- It includes organisms of related order. For example, chordates such as rats, dogs, bats, monkeys and camels belong to class Mammalia as they have similar characteristics such as hairy exoskeleton, mammary glands and external ears.

(vi) Phylum (in animals)/division (in plants)- Different classes having few common characteristics are placed in a single phylum. For example, all animals which have a notochord in the embryo belong to phylum chordata.

(vii) Kingdom- Organisms that share a set of distinguishing common characteristics are placed in the same kingdom.

Question 2

Question 2:
Briefly describe the importance of classification.

Accepted Answer

Answer:
Importance of classification

Classification is the method of organising or arranging organisms into separate groups on the basis of similarities and differences. It is a very important branch of science that deals with systematic arrangement of living organisms for further studies.

Classification of organisms is important because of the following reasons:

(i) It helps in studying wide variety of living organisms.
(ii) It provides a clear picture of all life forms before us.
(iii) It helps in understanding the inter-relationship among different groups of organisms.
(iv) It provides a base for the development of other biological sciences.

Question 3

Question 3:
What is hierarchy of categories? Describe the same.

Accepted Answer

Answer:
Hierarchy of categories refers to an arrangement of different taxonomic groups in a definite order from higher to lower categories. A category is called a taxon.The main aim of hierarchical taxonomy is to assign an organism an appropriate place within the systematic framework of classification.The categories or taxa in the hierarchy are placed in ascending order. As we move upwards from species to kingdom, the level of similarities between the organisms decreases.

The taxa or categories used in classifying plants and animals are:

(i) Species- It is the lowest category that includes individuals with similar morphological characters and reproduces to form offsprings.
(ii) Genus- It includes related species which have less characteristics in common.
(iii) Family- Group of related genera are included in a family. More similar genus groups are placed together in a single family.
(iv) Order- Families resembling one another in few characteristics are assembled in an order.
(v) Class- It includes organisms of related order.
(vi) Phylum (in animals)/division (in plants)- Different classes having few common characteristics are placed in a single phylum.
(vii) Kingdom- Organisms that share a set of distinguishing common characteristics are placed in the same kingdom.

Question 4

Question 4:
Write a note on kingdom Monera.

Accepted Answer

Answer:
Kingdom Monera: This kingdom includes prokaryotic and uniThe Fundamental Unit of Lifeular organisms. It includes bacteria, blue-green algae or cyanobacteria, and mycoplasma. This kingom is classified into the following sub-kingdoms:

1. Archaebacteria:
These are autotrophs, which obtain energy from the oxidation of chemical energy sources for their metabolic activities such as reduced gases like ammonia, methane or hydrogen sulphide. They produce their own amino acids and proteins.

They are divided into three groups:
(a) Methanogens- They produce methane by their metabolic activities. They cannot survive in the presence of oxygen.
(b) Thermoacidophiles- These archaea favour extremely hot and acidic environments. They use hydrogen sulphide as their energy source.
(c) Halophiles- They inhabit extremely salty and alkaline environments.

2. Eubacteria:
These are prokaryotic uniThe Fundamental Unit of Lifeular organisms which are enclosed in a porous, rigid The Fundamental Unit of Life wall. The plasma membrane surrounds a non-compartmentalised cytoplasm. The eubacteria lack membrane-bound The Fundamental Unit of Life organelles such as nucleus, mitochondria, Golgi apparatus etc. They possess a single, circular DNA which is coiled into one region of the The Fundamental Unit of Life, referred to as the nucleoid. They are divided into different categories on the basis of their body shape. These are:

(a) Bacilli (rod-shaped)
(b) Cocci (spherical)
(c) Spirilla (corkscrew)
(d) Vibrio (comma-shaped)

Electron transport and photosynthesis take place on the plasma membrane, which sometimes folds into the interior of the The Fundamental Unit of Life. The The Fundamental Unit of Life wall of eubacteria consists of a unique material called peptidoglycam which is composed of chains of sugars cross-linked by peptides. The eubacteria can be differentiated into two distinct types based on their The Fundamental Unit of Life wall composition - gram-positive bacteria and gram-negative bacteria. Many bacteria are also motile by means of appendages called flagella. Another set of appendages called pili help in sexual reproduction and attachment to the substrate.

Question 5

Question 5:
Describe the characteristics of kingdom Protista. Give two examples.

Accepted Answer

Answer:
Characteristics of Kingdom Protista:

(i) They include uniThe Fundamental Unit of Lifeular, eukaryotic organisms.
(ii) They may be free-living or parasitic or symbiotic in nature. Some also exist in colonies.
(iii) They may be autotrophic (e.g. algae and diatoms) or heterotrophic (protozoans).
(iv) They may be uninucleate, binucleate or multinucleate.
(v) Some of these organisms use appendages such as hair-like cilia or whip-like flagellum.
(vi) They reproduce asexually by binary fission or multiple fission and sexually by conjugation.

The Kingdom Protista is further classified into Phylum Protozoa:

(a) This phylum contains uniThe Fundamental Unit of Lifeular, mostly aquatic organisms.
(b) The body is either naked or covered by pellicle or hard shells. The body shape may also be varied.
(c) The cytoplasm is differentiated into an outer ectoplasm and an inner endoplasm.
(d) Locomotion is through finger-like pseudopodia, flagella or cilia.
(e) The protozoa undergo asexual reproduction by binary fission or multiple fission and sexual reproduction is by conjugation.

Phylum Protozoa is further divided into five classes:

Class 1- Mastigophora
Example : Euglena

Class 2- Sarcodina
Example : Amoeba

Class 3- Sporozoa
Example : Plasmodium

Class 4- Ciliata
Example : Paramecium

Class 5-Suctoria
Example : Ephelota

Question 6

Question 6:
Write a note on kingdom Fungi.

Accepted Answer

Answer:
Kingdom Fungi -

Fungi include heterotrophic, eukaryotic and non-photosynthetic organisms.

(a) Some fungi are known parasites, such as Puccinia, Albugo and Ustilago, and derive nutrition from hosts.
(b) Some fungi such as Mucor, Rhizopus, Penicillium and Agaricus are decomposers, saprophytes or saprobionts.

Fungi maybe uniThe Fundamental Unit of Lifeular (yeast) or filamentous. The body of a filamentous fungus is called a mycelium and it is composed of several thread-like structures called appendages. The Fundamental Unit of Life wall of fungi is composed of chitin and The Fundamental Unit of Lifeulose. Chitin is a tough complex of sugar.They store food in the form of glycogen. Fungi also exist in symbiotic association with algae, known as lichens. 
Certain fungi form a symbiotic association with an algal partner. This symbiotic association of fungi and algae is called a lichen. The algal component of the lichen is known as phycobiont and the fungal component of the lichen is known as mycobiont.

Question 7

Question 7:
Describe general characters, classification and example of old division Spermatophyta.

Accepted Answer

Answer:
General characteristics of old division spermatophyta:

(i) It includes higher plants that bear flowers and seeds.
(ii) The plants in this division have a sporophytic plant body with differentiated root, stem and leaves. The gametophytes are nutrition dependent on the sporophytes.
(iii) They have a well developed vascular system.
(iv) Plants have conspicuous, multiThe Fundamental Unit of Lifeular sex organs. Fertilisation does not require an external water source.
(v) Division spermatophyta was divided into following two subdivisions, depending upon whether the ovule was covered or naked and the presence of fruits. 
(a) Sub-division Gymnospermae
(b) Sub-division Angiospermae
Examples: Cycas, Pisum sativum, etc.

Question 8

Question 8:
Define pteridophytes. Compare between bryophytes and Pteridophytes.

Accepted Answer

Answer:
Pteridophytes include those plants that lack flowers and do not produce seeds. Their body is well differentiated into roots, stems and leaves. They have a well-developed vascular system with multiThe Fundamental Unit of Lifeular sex organs.

Examples of Pteridophytes- Selaginella, Dryopteris, Pteris, etc.

Comparison between bryophytes and pteridophytes:

Bryophytes
Pteridophyte

They have a gametophytic plant body.
They have a sporophytic plant body.

Sporophyte is parasitic over the gametophytic plant body throughout its life.
The gametophyte is small and independent.

Real stems and leaves are absent and the plant body is either thallose or folliose.
Real stems and leaves are present.

Plant body is fixed by rhizoids.
Plant body is fixed by roots.

They are non-vascular in nature.
They are vascular in nature.

Question 9

Question 9:
Explain general characteristics of phylum Platyhelminthes and Nematoda. Give two examples of each.

Accepted Answer

Answer:
General characteristics of Platyhelminthes:

(i) Their body is bilaterally symmetrical and dorsoventrally flattened.
(ii) They are acoelomate and triploblastic animals i.e. their tissues differentiate from three embryonic germ layers.
(iii) Circulatory and respiratory systems and skeleton are absent.
(iv) Their excretory system consists of blind tubules called protonephridia. Blind end of a tubule bears a tuft of cilia or a flagellum called the flame The Fundamental Unit of Life.
(v) They are hermaphrodites i.e. both male and female reproductive organs occur in the same individual.
Examples: Liver fluke (Fasciola) and blood fluke (Schistosoma)

General characters of Nematoda:

(i) They are bilaterally symmetrical, triploblastic, pseuodocoelomate and unsegmented animals.
(ii) They have a cylindrical or flattened, worm-like body. Their body is covered with a tough, resistant cuticle.
(iii) Sexes are separate.
(iv) Alimentary canal straight and complete with mouth and anus.
(v) Parasitic nematodes are pathogenic and are responsible for diseases such as elephantiasis (Wuchereria bancrofti),  ascariasis (Ascaris) and enterobiasis (Enterobius).

Question 10

Question 10:
Describe general characteristics of phylum Annelida. Give one example each class of Annelida.

Accepted Answer

Answer:
General characteristics of phylum Annelida:

(i) They are triploblastic, bilaterally symmetrical, soft, elongated and dorsoventrally flattened.
(ii) Their body is metamerically segmented externally by transverse grooves and internally by septa.
(iii) Their body is covered by thin cuticles and exoskeleton is absent.
(iv) They are true coelomates with closed blood vascular system. There is extensive organ differentiation.
(v) They have a tube-like alimentary canal, which is complete and extends straight from mouth to anus.
(vi) Reproduction is sexual. Sexes may be separate or united (hermaphrodite).
(vii) Segmented nephridia are present for excretion which removes wastes from coelom and blood stream directly to the exterior.
(viii) They are usually found in aquatic, marine or fresh-water habitats. Some are terrestrial and inhabit moist soil and some are free living forms.

Phylum Annelida is divided into three classes:
Class 1- Polychaeta
Example : Nereis.

Class 2- Oligochaeta
Example : Pheretima.

Class 3- Hirudinea
Example : Hirudinaria

Question 11

Question 11:
Explain the general charaters of phylum Mollusca. Give one example of following classes of Mollusca;
(i) Gastropoda;

(ii) Pelecypoda;
(iii) Cephalopoda.

Accepted Answer

Answer:
General characteristics of phylum Mollusca:

(a) They have a soft, bilaterally symmetrical body with little segmentation and without appendages.
(b) Body is divisible into an anterior head, a ventral foot and a dorsal visceral mass. The entire body is covered by a fold of thin skin called mantle, which secretes a hard calcareous shell of one or more pieces.
(c) Respiration occurs via gills, mantle or a "lung" of the mantle.
(d) Sexes are usually separate.
(e) They have an open circulatory system (except in cephalopods). The body cavity is haemocoel and the true coelom is reduced and restricted to the pericardial cavity and the lumen of the gonads and nephridia.
(f) Some species have sensory organs of touch, smell, taste and vision.
(g) They excrete via metanephridia or kidneys.
(h) The molluscs are aquatic, mostly marine with a few freshwater and terrestrial forms.

Examples:
(i) Class Gastropoda: Pila (apple snail)
(ii) Class Pelecypoda: Teredo (ship worm)
(iii) Class Cephalopoda: Octopus

Question 12

Question 12:
Explain the general characters of phylum Arthropoda. Give one example of following classes
(i) Crustacea;

(ii) Myriapoda;
(iii) Insecta;

(iv) Arachnida.

Accepted Answer

Answer:
General characteristics of phylum Arthropoda:

(a) They are triploblastic, bilaterally symmetrical and metamerically segmented animals.
(b) Body segments are grouped into two regions - cephalothorax and abdomen or three regions - head, thorax and abdomen. 
(c)Body cavity is haemocoel and the coelom is reduced to the spaces of the genital and excretory organs.
(d) They have a complete alimentary canal, with mouth and anus lying opposite each other.
(e) Sexes are separate. Sexual dimorphism is well marked in several forms. Fertilisation is usually internal, oviparous or ovoviviparous and often with metamorphosis.
(f) They have gills, trachea or book-lungs for respiration.
(g) They lack true nephridia and excretion occurs via coelomoducts, malpighian tubules or green or coxal glands.
(h) Circulatory system is open with dorsal heart, arteries and haemocoel but without capillaries and veins.
(i) Their exoskeleton comprises cuticle containing protein, lipid, chitin. Often, calcium carbonate is secreted by underlying epidermis and shed at intervals.

Examples:
(i) Class Crustacea: Palaemon
(ii) Class Myriapoda: Scolopendra
(iii) Class Insecta: Lepisma
(iv) Class Arachnida: Sarcoptes

Question 13

Question 13:
Name major phyla of Animal kingdom. Write down one character and one example of each of them.

Accepted Answer

Answer:
Kingdom Animalia has been classified into 11 major phylums. These are:

1. Phylum Porifera:  
These are the simplest, multiThe Fundamental Unit of Lifeular, diploblastic, asymmetrical or radially symmetrical animals. Example: Sycon.

2. Phylum Cnidaria or Coelenterata:
These are diploblastic, radially symmetrical organisms with tissue level of organisation. Example: Hydra.

3. Phylum Ctenophora: 
They are bilaterally symmetrical, triploblastic animals with eight longitudinal rows of ciliary comb-plates for locomotion.
Example: Pleurobrachia.

4. Phylum Platyhelminthes:
They are bilaterally symmetrical, triploblastic, acoelomate and hermaphrodite animals.
Example: Taenia solium.

5. Phylum Nematoda:
They are bilaterally symmetrical, triploblastic, pseudocoelomate and unsegmented animals.
Example: Ascaris.

6. Phylum Annelida:
They are bilaterally symmetrical, triploblastic, true coelomate animals.
Example: Hirudinaria.

7. Phylum Arthropoda:
They are triploblastic, bilaterally symmetrical, haemocoelomate animals with metamerically segmented body.
Example: Palaemon.

8. Phylum Mollusca:
They are bilaterally symmetrical, haemocoelomate animals with little segmentation.
Example: Chiton.

9. Phylum Echinodermata
They are triploblastic, coelomate, radially symmetrical animals with spiny hard calcareous endoskeleton.
Example: Antedon.

10. Phylum Hemichordata
They are bilaterally symmetrical animals with unsegmented body and have gill slits for respiration.
Example: Balanoglossus.

11. Phylum Chordata:
They possess dorsal, hollow, tubular nerve cord with a presence of notochord and paired gill-slits in the pharynx.
Example: Herdmania.

Question 14

Question 14:
Describe the important characters of mammals and birds. Give two examples of each.

Accepted Answer

Answer:
Characteristics of mammals:

(i) Mammals are warm-blooded vertebrates. Their body is divisible into head, trunk, neck and tail. Movable eyelids are present.
(ii) Females have mammary glands that secrete milk for the nourishment of the young.
(iii) A muscular diaphragm separates thoracic and abdominal cavities.
(iv) Respiration is through lungs only and the heart is four-chambered. Mammals possess non-nucleated biconcave red blood corpuscles.
(v)Fertilisation is internal, and mammals are known to be viviparous.
(vi)Two pairs of pentadactyl limbs are present. Teeth are thecodont and heterodont. Fleshy external ear (pinnae) is present.
(vii) Hair and subcutaneous fat forms an insulating layer. Cutaneous glands such as sweat glands, scent glands and sebaceous glands are present.
Example: Macropus and Rattus.

Characteristics of  birds:
(i) Warm-blooded, tetrapodous vertebrates. 
(ii) Forelimbs are modified into wings for flight, whereas the hind limbs bear four clawed digits and are adapted for walking, perching or swimming.
(iii) Their bones are light and spongy due to presence of air cavities.
(iv) They excrete semi-solid urine with uric acid. They do not possess a bladder.
(v) Horny scales are present on the feet but most of the body is covered by feathers.
(vi) Birds undergo internal fertilisation and are oviparous.
(vii) Their narrow jaws form a horny beak which is modified for different purposes. Teeth are absent.
(viii) They breathe through lungs and have a four-chambered heart.

Examples: Gallus and Columba.

Question 15

Question 15:
What are pisces? Classify and explain two different kinds of fishes by the help of suitable examples.

Accepted Answer

Answer:
Pisces is a super class of subphylum Gnathostomata, which consists of following two classes:

Class 1: Chondrichthyes
(a) Marine fishes with entirely cartilaginous endoskeleton.
(b) They have a streamlined body that is either compressed laterally or flattened dorsoventrally.
(c) Mouth is ventral in position.
(d) Skin is tough and covered with minute placoid scales.
(e) Respiration occurs via gills.
Examples: Scoliodon and Torpedo

Class 2: Osteichthyes:
(a) Marine and fresh-water fish with partial or full bony endoskeleton.
(b) Their size varies from 10 mm to 4 metres.
(c) They have a spindle-shaped body.
(d) Four pairs of gills are present for respiration.
(e) They excrete ammonia (ammonotelic animals).
Examples: Labeo and Protopterus.

Chapter 5 : Why Do We Fall Ill